Perchlorate: questions and answers.
Perchlorate is both a naturally occurring and a manmade chemical. Naturally occurring perchlorate is found, for example, in nitrate fertilizer deposits from Chile. Most of the perchlorate manufactured in the United States is used as the primary ingredient in solid rocket propellant. Perchlorate also is used in a wide variety of industrial processes, including, but not limited to, tanning and leather finishing, rubber manufacture, paint and enamel production, and production of additives for lubricating oils. In addition, perchlorate is used in pyrotechnics such as fireworks, gunpowder, explosives, and highway flares. Wastes from the manufacture and improper disposal of perchlorate-containing chemicals are increasingly being discovered in soil, groundwater, drinking water, and irrigation water around the country.
The Food and Drug Administration (FDA) recognizes the potential for perchlorate contamination of food and feed from the use of contaminated waters such as irrigation water, processing water, and source waters for bottled drinking water. Therefore, FDA has begun to determine the occurrence of perchlorate in a variety of foods to evaluate exposure to perchlorate from food and to support any action that might be needed to protect the public's health.
What are the effects of perchlorate on the human body?
At high doses, perchlorate can interfere with iodide uptake into the thyroid gland, disrupting the gland's functions. In fact, perchlorate has been used as a drug to treat hyperthyroidism and to diagnose disorders related to thyroid or iodine metabolism. In adults, the thyroid helps to regulate metabolism. In children, the thyroid plays a major role in proper development in addition to metabolism. Impairment of thyroid function in expectant mothers may affect the fetus and newborn, and effects may include delayed development and decreased learning capability. Chronic lowering of thyroid hormones due to high perchlorate exposure also may result in thyroid gland tumors.
Has a safe level been established for perchlorate in water and food?
In the summer of 2003, the Administration asked the National Academy of Sciences (NAS) to review several important questions related to whether perchlorate is a public health concern. The NAS study will be a major factor in determining if some levels of perchlorate in food are a public health concern.
Guidance issued by the U.S. Environmental Protection Agency (U.S. EPA) in 1999 set health risk thresholds using a reference dose (RfD) range of 7-35 micrograms per day ([micro]g/day) for a 70-kilogram (70-kg) adult. This guidance remains in effect pending the outcome of the NAS study. U.S. EPA, which regulates drinking-water safety, has issued a draft reference dose (RfD) of 2.1 [micro]g/day for a 70-kg adult as part of a draft perchlorate health risk assessment.
The RfD is an estimate of the daily dose below which risks would be considered negligible for a lifetime exposure. U.S. EPA will not finalize its draft health risk assessment nor establish the final RfD until after the NAS review, which should be completed by December 2004. More information on the U.S. EPA analysis and the health effects of perchlorate, as well as U.S. EPA's interim guidance, can be found at www.epa.gov/swerffrr/documents/perchlorate_qa.htm and www.epa.gov/safewater/ccl/perchlorate/perchlo.html.
Recent studies have shown the presence of perchlorate in milk. Has FDA found perchlorate in milk?
As part of its research and method development, FDA has tested 20 research milk samples from various regions of the country, including California, in order to begin to understand the extent to which perchlorate occurs in milk. Perchlorate levels ranged from 3 to 11 parts per billion (ppb). FDA notes that this is a very limited set of data; however, these values are similar to those already reported in the literature. In September 2003, a Texas Tech University study found perchlorate levels ranging from 1.7 to 6.4 ppb in seven fluid milk samples and 1.1 ppb in one evaporated milk sample. Perchlorate levels ranging from 1.5 ppb to 10.6 ppb were measured by the California Department of Food and Agriculture in California milk, and levels ranging from nondetectable to 3.6 ppb in California milk samples were reported by the Environmental Working Group in June 2004.
Do lettuce and other foods contaminated with perchlorate present a health risk?
At this time, further studies are needed to determine the health risk associated with exposure to perchlorate from foods. FDA currently has no evidence to recommend that consumers should alter their infants' and children's diets and eating habits to avoid exposure to perchlorate. The NAS review of U.S. EPA's RfD will be a major factor in determining if some levels of perchlorate in food are a public health concern. FDA is continuing to work with other federal agencies, such as the U.S. Department of Agriculture and U.S. EPA, to determine the risk associated with perchlorate exposure and the occurrence of perchlorate in foods. If an elevated health risk is determined, FDA will seek ways to reduce dietary exposure to perchlorate.
U.S. EPA's draft drinking-water range for perchlorate is 4-18 parts per billion (ppb). Is this the allowable level of perchlorate in bottled water?
U.S. EPA's draft drinking-water range of 4-18 ppb for perchlorate is based on 2 liters of daily consumption and its provisional RfD range of 0.1-0.5 micrograms per kilogram per day (7-35 [micro]g/day for a 70-kg adult). The agency has not yet set an allowable level, or maximum contaminant level (MCL), for perchlorate in drinking water.
U.S. EPA is gathering data on health effects, occurrence in public water systems, analytical methods, and treatment techniques with respect to perchlorate; these data will be used to decide if a national drinking-water standard is warranted.
If U.S. EPA establishes a standard--that is, an MCL--for perchlorate in public drinking water, FDA will establish an allowable level for perchlorate under the quality standard regulations for bottled water.
In some areas of California, perchlorate has been found in drinking water or tap water. Do bottled-water manufacturers test for perchlorate?
FDA has not established a standard for perchlorate in bottled water, and its current bottled-water regulations do not require bottled-water manufacturers to test for perchlorate. If U.S. EPA establishes a standard for perchlorate in public drinking water, FDA will establish a quality standard for perchlorate in bottled water, which will result in bottlers being required to test for perchlorate.
The bottled-water industry is aware of the potential for perchlorate contamination in source waters for bottling, and some bottlers may voluntarily test for perchlorate. Consumers should contact the producers of their favorite brands for more information.
Is the government planning to test bottled-water samples for perchlorate?
FDA is analyzing bottled-water samples from various regions of the country as part of an initial survey assignment issued in December of 2003. In addition, a small survey of eight imported and eight domestic bottled waters reported by U.S. EPA and Oak Ridge laboratory in 2000 found that none of the bottled-water samples contained perchlorate above the detection limit of 5 ppb (parts per billion) for perchlorate in water.
(Adapted from "Perchlorate: Questions and Answers," FDA/Center for Food Safety and Applied Nutrition/Office of Plant & Dairy Foods, updated June 2004, www.cfsan.fda.gov/~dms/clo4qa.html.)
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|Title Annotation:||Technical Briefs|
|Publication:||Journal of Environmental Health|
|Date:||Nov 1, 2004|
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